The present application relates to semiconductor technology and more particularly to a method of forming semiconductor fins on an oxide layer that is formed into a bulk semiconductor substrate. The present application also relates to a semiconductor structure that is formed by the method of the present application.
For more than three decades, the continued miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) has driven the worldwide semiconductor industry. Various showstoppers to continued scaling have been predicated for decades, but a history of innovation has sustained Moore's Law in spite of many challenges. However, there are growing signs today that metal oxide semiconductor transistors are beginning to reach their traditional scaling limits. Since it has become increasingly difficult to improve MOSFETs and therefore complementary metal oxide semiconductor (CMOS) performance through continued scaling, further methods for improving performance in addition to scaling have become critical.
The use of non-planar semiconductor devices such as, for example, semiconductor fin field effect transistors (finFETs) is the next step in the evolution of complementary metal oxide semiconductor (CMOS) devices. Semiconductor fin field effect transistors (FETs) can achieve higher drive currents with increasingly smaller dimensions as compared to conventional planar FETs.
In order to electrically isolate finFETs from the underlying substrate, finFETs may be fabricated from a semiconductor-on-insulator (SOI) substrate, where the semiconductor fin may be separated from a base substrate by a buried insulator layer. FinFETs may also be fabricated from bulk semiconductor substrates to reduce wafer cost and/or enable formation of certain devices in the bulk substrate. However, the fins of finFETs fabricated from bulk semiconductor substrates are typically not electrically isolated from the bulk semiconductor substrate, potentially resulting in reduced device performance.
One method of forming fins that are electrically isolated from the bulk semiconductor substrate includes a bottom oxidation process. In such a process, semiconductor fins are formed within an upper semiconductor material portion of a bulk semiconductor substrate and thereafter oxidation is performed to provide an oxide region beneath each of the semiconductor fins. The aforementioned prior art process suffers from random semiconductor fin tilting. That is, the prior art bottom oxidation process may cause some of the semiconductor fins to be less than perpendicularly aligned to a horizontal surface of the substrate. Such fin titling, even if only a couple of degrees, may be problematic for future technology nodes.